Chlamydia trachomatis is a major cause of pelvic inflammatory disease which often leads to tubal obstruction and infertility. Because of difficulty in diagnosing Chlamydia-induced salpingitis and the inability to obtain appropriate clinical specimens of fallopian tubes, the pathogenesis of salpingitis and its sequelae remains unclear. In this proposal, the guinea pig model of chlamydial genital infection will be used to investigate pathogenic mechanisms and factors which lead to upper genital tract pathology. In this model, normal guinea pigs infected intravaginally with the Chlamydia psittaci agent of guinea pig inclusion conjunctivitis (GPIC) develop ascending infections resulting in endometritis, salpingitis and long-term oviduct pathology comparable in cellular composition and percentage of cases to that seen in humans. Both non-immunological and immunological mechanisms appear to be involved in the production of upper genital tract pathology. Since tumor necrosis factor alpha (TNF-alpha) appears in genital secretions concomitant with the acute inflammatory response, a major focus will be on the factors which elicit TNF-alpha production, such as chlamydial elementary bodies themselves, LPS, and NK cells, and on the role of TNF-alpha in production of pathologic changes. The effect of TNF-alpha on transforming growth factor production, integrin expression, and the acute inflammatory response will be evaluated. The role of the alternative complement pathway in the generation of TNF-alpha will also be explored using C3-deficient guinea pigs. Since the incidence of tubal disease has been found in this model to be associated with the stage of the estrous cycle in which animals are infected, studies will be undertaken to confirm the role of estrogen and to determine whether estrogen influences the production of TNF-alpha and the expression of integrins which can mediate inflammation. Enhanced disease is also associated with repeated infections and appears to be related to a delayed-type hypersensitivity reaction in this model. Studies will be done to characterize the role of the T cell in the development of upper tract pathology resulting from repeated infection, including the phenotyping and determination of antigen-specificity of the T cell response in the genital tract. Particular emphasis will be on the role of the chlamydial heat shock protein (Hsp60) in the development of immunopathology. Hsp60-specific T cell lines will be developed and used in adoptive transfer experiments to confirm the role of this protein. Since previous results have indicated that immunization to prevent upper tract pathology is feasible, further experiments will be performed to establish this approach as a achievable strategy and to determine at what point it interferes with the development of pathology. Since the major outer membrane protein was effective in reducing infection, it will be evaluated for its effectiveness in preventing upper genital tract pathology. The newly developed phage epitope display technology will also be used to generate potential conformational epitopes for testing as vaccine candidates in this model.